Download ocaml

Functional Programming
Language
OCaml Tutorial
科大-耶鲁联合研究中心
http://kdyhcs.ustcsz.edu.cn
Outline
 Introduction
 Get Started
 OCaml Basis
 Basic Concepts
 Examples
 Discussion
Introduction
• Functional programming(FP) emphasizes
application of functions and has its roots in
lambda calculus
• The difference between function in FP and
imperative languages is side effects
• FP can also be accomplished in imperative
languages.
History
• 1950s
• 1960s
• 1970s
• 1980s
• 1987
LISP
APL -> J -> K
ML -> Objective Caml , Standard ML
Dependent Types -> Coq, Agda, Epigram
Haskell
Get Started
• Install
• http://caml.inria.fr/pub/distrib/ocaml-3.11/ocaml-3.11.0win-msvc.exe
• Interactive
• Run “ocaml”
• Objective Caml version 3.11.2
• # 1+2;;
• - : int =3
• Use any text editor
• Emacs/Vim
• Notepad++ …
Get Started
• Run Emacs
• Visist New File -> “test.ml”
• Short Keys
• C-c C-s
• C-c C-b
• C-c C-r
• Tab
• Demo
“start ocaml”
“eval whole file”
“eval selected code”
“Ident”
OCaml
• Declaring Variables
• Variables in OCaml are immutable!
• Declaring Functions
• OCaml functions don’t have explicit “return”. The
return value is the last statement.
OCaml
• All functions and values in OCaml have a datatype
• let add x y = (x + y);;
• OCaml will report
• val add : int -> int -> int = <fun>
• which means
• function “add” takes two “int” inputs and return a “int”
• Generic Function
• let fst x y = x
• - val fst : 'a -> 'b -> 'a = <fun>
• # fst 1 2 ;;
• # fst "a" "b";;
• # fst "a" 1;;
Recursion and Nested Function
Pattern Match
• Example
• Patterns can be chained together
High-order Functions
• A high-order function is a functions that takes
another function as a parameter or a function
returns another function or both.
• Function can be partial applied
• add : int -> int -> int
• add 1 : int -> int
• add 1 2 : int
• let f = add 1
• let result = f 2
High-order Functions
• Composition
• let double x = x * 2
• let power x = x * x
• let compose f g x = g (f x)
• let result = (compose double power) 4
• Pipeline
• let pipe x f = f x
• let result = (pipe (pipe 4 double) power)
Anonymous Function
• Example
• fun x -> x * 2
• We can rewrite examples from Page 11
• compose (fun x->x*2) (fun x->x*x) 4
• Much use of anonymous functions
Data Structures
• Option Type
• Tuples
• List
Examples
• Fibonacci number
• List filter, map, fold
Lab
• Write a calculator
• Provided parser combinators
• built-in parsers
• integer, alpha, ident, char, string
• combinators
• many, sepBy, paren, chainl
• infix
• >>
>>=
<|>
<?>
• #use “parsec.ml”;;
Lab
• Grammar
• Exp :: Term [+-] Term
• Term :: Factor [*/] Factor
• Factor :: int | ( Exp )
• Get Start
• let add = (char ‘+’) >> (return (+)) <?> “+”
• Receive a char ‘+’ and return function (+) with possible error
message “+”
• let factor = (paren exp) <|> (integer <?> “integer”)
• either a parened “exp” or an integer
• let term = chainl factor (mul <|> div)
• a list of factor chained with “mul” or “div”
• let expr = chainl term (add <|> sub)
Lab
• Write a parser for first-order logic formula
• Formula :: Clause \/ Clause
• Clause
:: Term /\ Term
• Term
:: Literal | Literal Comp Literal
• Literal
:: id | int | bool
• Eval the formula with given environment
• (x:true;y:false;….)
TODO
• Spec#
• ESC/Java
• Compcert
• CComp